Catalysts

ABSTRACT

The present invention relates to novel metallocene catalysts of formula I, which is defined herein. The present invention also provides processes for making these catalysts and their use in olefin polymerisation reactions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national counterpart application of PCTInternational Application Serial No. PCT/GB2010/051791, filed Oct. 25,2010, which claims priority to GB Patent Application Serial Number0918736.0, filed Oct. 26, 2009, the entire disclosures of both whichapplications are hereby incorporated herein by reference.

TECHNICAL FIELD

This invention relates to catalysts. More specifically, the presentinvention relates to particular metallocene procatalysts, and the use ofsuch procatalysts in polyolefin polymerization reactions.

BACKGROUND

It is well known that ethylene (and α-olefins in general) can be readilypolymerized at low or medium pressures in the presence of certaintransition metal catalysts. These catalysts are generally known asZeigler-Natta type catalysts.

A particular group of these Zeigler-Natta type catalysts, which catalysethe polymerization of ethylene (and α-olefins in general), comprise analuminoxane activator and a metallocene transition metal catalyst.Metallocenes comprise a metal bound between two η⁵-cyclopentadienyl typeligands. Generally the η⁵-cyclopentadienyl type ligands are selectedfrom η⁵-cyclopentadienyl, η⁵-indenyl and η⁵-fluorenyl.

It is also well known that these η⁵-cyclopentadienyl type ligands can bemodified in a myriad of ways. One particular modification involves theintroduction of a linking group between the two cyclopentadienyl ringsto form ansa-metallocenes.

Numerous ansa-metallocenes of transition metals are known in the art.However, there remains a need for improved ansa-metallocene catalystsfor use in polyolefin polymerization reactions. In particular, thereremains a need for new metallocene catalysts with high polymerizationactivities/efficiencies.

There is also a need for catalysts that can produce polyethylenes withparticular characteristics. For example, catalysts capable of producinglinear high density polyethylene (LHDPE) with a relatively narrowdispersion in polymer chain length are desirable.

Accordingly, it is an object of the present invention to provideimproved ansa-metallocene catalysts.

BRIEF SUMMARY OF THE DISCLOSURE

In a first aspect, the present invention provides a compound of theformula I shown below

wherein:

R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂ are eachindependently selected from hydrocarbyl, carbocyclyl or heterocyclyl,each of which is optionally substituted;

Q is a bridging group;

X is selected from zirconium, titanium or hafnium;

Y is selected from halo, hydride, a phosphonated or sulfonated anion, ora (1-6C)alkyl, (1-6C)alkoxy, aryl or aryloxy group which is optionallysubstituted with halo, nitro, amino, phenyl, (1-6C)alkoxy, orSi[(1-4C)alkyl]₃.

It has surprisingly been found that the compounds of the presentinvention possess particularly high catalytic performance when used forthe polymerization of polyethylene.

In a further aspect, the present invention provides a process forsynthesizing a compound of formula I as defined herein.

In a further aspect, the present invention provides the use of acompound of formula I as defined herein as a procatalyst for thesynthesis of polyolefins (e.g. polyethylene).

In a further aspect, the present invention provides a process for thepolymerization of olefin monomers (e.g. ethylene) comprising reactingthe olefin monomers in the presence of a compound of formula I asdefined herein and suitable activator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows four views of rac-EBI*ZrCl₂, with H atoms omitted forclarity and thermal ellipsoids drawn at 50%;

FIG. 2 shows alternate views of meso-EBI*ZrCl₂, with H atoms and toluenemolecule omitted for clarity and thermal ellipsoids drawn at 50% (secondview shows the location of the toluene molecule);

FIG. 3 shows four views of rac-EBI*HfCl₂, with H atoms omitted forclarity and thermal ellipsoids drawn at 50%; and

FIG. 4 shows four views of meso-EBI*HfCl₂, with H atoms omitted forclarity and thermal ellipsoids drawn at 50%.

DETAILED DESCRIPTION Definitions Hydrocarbyl

The term “hydrocarbyl” as used herein includes reference to moietiesconsisting exclusively of hydrogen and carbon atoms; such a moiety is analiphatic moiety. The moiety may, for example, comprise 1, 2, 3, 4, 5,6, 7, 8, 9, 10, 11 or 12 carbon atoms. Examples of hydrocarbyl groupsinclude C₁₋₆ alkyl (e.g. C₁, C₂, C₃ or C₄ alkyl, for example methyl,ethyl, propyl, isopropyl, n-butyl, sec-butyl or tert-butyl); alkenyl(e.g. 2-butenyl); and alkynyl (e.g. 2-butynyl) and the like.

Alkyl

The term “alkyl” as used herein include reference to a straight orbranched chain alkyl moieties, typically having 1, 2, 3, 4, 5 or 6carbon atoms. This term includes reference to groups such as methyl,ethyl, propyl (n-propyl or isopropyl), butyl (n-butyl, sec-butyl ortert-butyl), pentyl, hexyl and the like. In particular, an alkyl mayhave 1, 2, 3 or 4 carbon atoms.

Alkoxy

The term “alkoxy” as used herein include reference to —O-alkyl, whereinalkyl is straight or branched chain and comprises 1, 2, 3, 4, 5 or 6carbon atoms. In one class of embodiments, alkoxy has 1, 2, 3 or 4carbon atoms. This term includes reference to groups such as methoxy,ethoxy, propoxy, isopropoxy, butoxy, tert-butoxy, pentoxy, hexoxy andthe like.

Carbocyclyl

The term “carbocyclyl” as used herein includes reference to a saturated(e.g. cycloalkyl) or unsaturated (e.g. aryl) ring moiety having 3, 4, 5,6, 7, 8, 9 or 10 ring carbon atoms. In particular, carbocyclyl includesa 3- to 10-membered ring or ring system and, in particular, a 6-memberedring, which may be saturated or unsaturated. A carbocyclic moiety is,for example, selected from cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, norbornyl, bicyclo[2.2.2]octyl, phenyl, naphthyl, and thelike.

Cycloalkyl

The term “cycloalkyl” as used herein includes reference to an alicyclicmoiety having 3, 4, 5, 6, 7 or 8 carbon atoms. The group may be abridged or polycyclic ring system. More often cycloalkyl groups aremonocyclic. This term includes reference to groups such as cyclopropyl,cyclobutyl, cyclopentyl, cyclohexyl, norbornyl, bicyclo[2.2.2]octyl andthe like.

Aryl

The term “aryl” as used herein includes reference to an aromatic ringsystem comprising 6, 7, 8, 9 or 10 ring carbon atoms. Aryl is oftenphenyl but may be a polycyclic ring system, having two or more rings, atleast one of which is aromatic. This term includes reference to groupssuch as phenyl, naphthyl and the like.

Heterocyclyl

The term “heterocyclyl” as used herein includes reference to a saturated(e.g. heterocycloalkyl) or unsaturated (e.g. heteroaryl) heterocyclicring moiety having from 3, 4, 5, 6, 7, 8, 9 or 10 ring atoms, at leastone of which is selected from nitrogen, oxygen, phosphorus, silicon andsulphur. In particular, heterocyclyl includes a 3- to 10-membered ringor ring system and more particularly a 5- or 6-membered ring, which maybe saturated or unsaturated.

A heterocyclic moiety is, for example, selected from oxiranyl, azirinyl,1,2-oxathiolanyl, imidazolyl, thienyl, furyl, tetrahydrofuryl, pyranyl,thiopyranyl, thianthrenyl, isobenzofuranyl, benzofuranyl, chromenyl,2H-pyrrolyl, pyrrolyl, pyrrolinyl, pyrrolidinyl, imidazolyl,imidazolidinyl, benzimidazolyl, pyrazolyl, pyrazinyl, pyrazolidinyl,thiazolyl, isothiazolyl, dithiazolyl, oxazolyl, isoxazolyl, pyridyl,pyrazinyl, pyrimidinyl, piperidyl, piperazinyl, pyridazinyl,morpholinyl, thiomorpholinyl, especially thiomorpholino, indolizinyl,isoindolyl, 3H-indolyl, indolyl, benzimidazolyl, cumaryl, indazolyl,triazolyl, tetrazolyl, purinyl, 4H-quinolizinyl, isoquinolyl, quinolyl,tetrahydroquinolyl, tetrahydroisoquinolyl, decahydroquinolyl,octahydroisoquinolyl, benzofuranyl, dibenzofuranyl, benzothiophenyl,dibenzothiophenyl, phthalazinyl, naphthyridinyl, quinoxalyl,quinazolinyl, quinazolinyl, cinnolinyl, pteridinyl, carbazolyl,β-carbolinyl, phenanthridinyl, acridinyl, perimidinyl, phenanthrolinyl,furazanyl, phenazinyl, phenothiazinyl, phenoxazinyl, chromenyl,isochromanyl, chromanyl and the like.

Heteroaryl

The term “heteroaryl” as used herein includes reference to an aromaticheterocyclic ring system having 5, 6, 7, 8, 9 or 10 ring atoms, at leastone of which is selected from nitrogen, oxygen and sulphur. The groupmay be a polycyclic ring system, having two or more rings, at least oneof which is aromatic, but is more often monocyclic. This term includesreference to groups such as pyrimidinyl, furanyl, benzo[b]thiophenyl,thiophenyl, pyrrolyl, imidazolyl, pyrrolidinyl, pyridinyl,benzo[b]furanyl, pyrazinyl, purinyl, indolyl, benzimidazolyl,quinolinyl, phenothiazinyl, triazinyl, phthalazinyl, 2H-chromenyl,oxazolyl, isoxazolyl, thiazolyl, isoindolyl, indazolyl, purinyl,isoquinolinyl, quinazolinyl, pteridinyl and the like.

Halogen

The term “halogen” or “halo” as used herein includes reference to F, Cl,Br or I. In an embodiment, a halogen is F, Cl or Br. In many instances,a halogen will be Cl.

Substituted

The term “substituted” as used herein in reference to a moiety meansthat one or more, especially up to 5, more especially 1, 2 or 3, of thehydrogen atoms in said moiety are replaced independently of each otherby the corresponding number of the described substituents. The term“optionally substituted” as used herein means substituted orunsubstituted.

It will, of course, be understood that substituents are only atpositions where they are chemically possible, the person skilled in theart being able to decide (either experimentally or theoretically)without inappropriate effort whether a particular substitution ispossible. For example, amino or hydroxy groups with free hydrogen may beunstable if bound to carbon atoms with unsaturated (e.g. olefinic)bonds. Additionally, it will of course be understood that thesubstituents described herein may themselves be substituted by anysubstituent, subject to the aforementioned restriction to appropriatesubstitutions as recognised by the skilled man.

Catalytic Compounds

As stated above, the present invention provides a compound of theformula I shown below

wherein:

R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂ are eachindependently selected from hydrocarbyl, carbocyclyl or heterocyclyl,each of which is optionally substituted;

Q is a bridging group;

X is selected from zirconium, titanium or hafnium; and

each Y is selected from halo, hydride, a phosphonated or sufonatedanion, or a (1-6C)alkyl, (1-6C)alkoxy, aryl or aryloxy group which isoptionally substituted with halo, nitro, amino, phenyl, (1-6C)alkoxy, orSi[(1-4C)alkyl]₃.

It will be appreciated that the structural formula I presented above isintended to show the substituent groups in a clear manner. A morerepresentative illustration of the spatial arrangement of the groups isshown in the alternative representation below:

In an embodiment, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂are each independently selected from a hydrocarbyl, carbocyclyl orheterocyclyl group, each of which is optionally substituted by halo,amino, nitro, cyano, (1-6C)alkyl, (1-6C)alkoxy, (1-6C)alkylamino,[(1-6C)alkyl]₂amino, or —S(O)_(r)(1-6C)alkyl (where r is 0, 1 or 2).

In an embodiment, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂are each independently selected from a hydrocarbyl or aryl group, eachof which is optionally substituted by halo, amino, nitro, cyano,(1-6C)alkyl, (1-6C)alkoxy, (1-6C)alkylamino, [(1-6C)alkyl]₂amino, or—S(O)_(r)(1-6C)alkyl (where r is 0, 1 or 2).

In an embodiment, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂are each independently selected from (1-6C)alkyl or phenyl, each ofwhich is optionally substituted by halo, amino, nitro, cyano,(1-6C)alkyl, (1-6C)alkoxy, (1-6C)alkylamino, [(1-6C)alkyl]₂amino, or—S(O)_(r)(1-6C)alkyl (where r is 0, 1 or 2).

In an embodiment, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂are (1-6C)alkyl groups that are optionally substituted by halo, amino,nitro, cyano, (1-6C)alkyl, (1-6C)alkoxy, (1-6C)alkylamino,[(1-6C)alkyl]₂amino, or —S(O)_(r)(1-6C)alkyl (where r is 0, 1 or 2).

In an embodiment, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂are (1-6C)alkyl.

In an embodiment, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂are (1-4C)alkyl.

In an embodiment, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂are (1-2C)alkyl.

In an embodiment, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂are all methyl.

In an embodiment, R₁ and R₇, R₂ and R₈, R₃ and R₉, R₄ and R₁₀, R₅ andR₁₁, and R₆ and R₁₂ are the same.

Suitably, Q is a bridging group comprising 1, 2 or 3 bridging atomsselected from C, N, O, S, Ge, Sn, P, B or Si, or a suitable combinationthereof. The bridging group Q may also optionally bear one or moresubstituent groups, for example, one or more hydroxyl, (1-6C)alkyl,(1-6C)alkoxy or aryl groups.

Suitably Q is a group of the formula —[C(R^(a)R^(b))]_(n)— wherein n is2 or 3 and R^(a) and R^(b) are each independently hydrogen, (1-6C)alkylor (1-6C)alkoxy.

In an embodiment, Q is —CH₂—CH₂— or —CH₂—CH₂—CH₂—.

In a particular embodiment, Q is —CH₂—CH₂—.

In an embodiment, X is zirconium or hafnium.

In a particular embodiment, X is zirconium.

In a particular embodiment, X is hafnium.

In an embodiment, each Y group is the same.

In an embodiment, Y is selected from halo, (1-6C)alkyl or phenyl,wherein the alkyl or phenyl group is optionally substituted with halo,nitro, amino, phenyl, (1-6C)alkoxy, or Si[(1-4C)alkyl]₃.

In an embodiment, Y is selected from halo or a (1-6C)alkyl group whichis optionally substituted with halo, nitro, amino, phenyl, (1-6C)alkoxy,or Si[(1-4C)alkyl]₃.

In another embodiment, Y is selected from halo or a (1-6C)alkyl groupwhich is optionally substituted with halo, phenyl, or Si[(1-2C)alkyl]₃.

In another embodiment, Y is selected from chloro, bromo, or a(1-4C)alkyl group which is optionally substituted with halo, phenyl, orSi[Me]₃.

In a particular embodiment, Y is selected from chloro or a (1-4C)alkylgroup which is optionally substituted with phenyl or Si[Me]₃.

In a further embodiment, Y is chloro, bromo or methyl.

In a further embodiment, Y is chloro or bromo.

In a further embodiment, Y is chloro.

In another embodiment, Y is methyl.

In an embodiment, the compound of the present invention has thestructural formula II shown below

wherein:

R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁, R₁₂, X and Y are each asdefined hereinbefore.

In an embodiment, the compound of the present invention has thestructural formula III shown below

wherein:

R₁, R₂, R₃, R₄, R₅, R₆, X and Y are each as defined hereinbefore.

In an embodiment, the compound has the structural formula IV shown below

wherein:

X and Y are as defined hereinbefore.

In a particular group of compounds of formula IV, X is zirconium orhafnium.

In a further group of compounds of formula IV, X is zirconium.

In a further group of compounds of formula IV, X is hafnium.

In a particular group of compounds of formula IV, each Y group is thesame.

In a further group of compounds of formula IV, Y is selected from halo,(1-6C)alkyl or phenyl, wherein the alkyl or phenyl group is optionallysubstituted with halo, nitro, amino, phenyl, (1-6C)alkoxy, orSi[(1-4C)alkyl]₃.

In a further group of compounds of formula IV, Y is selected from haloor a (1-6C)alkyl group which is optionally substituted with halo, phenylor Si[(1-2C)alkyl]₃.

In a particular group of compounds of formula IV, Y is selected fromchloro, bromo or a (1-4C)alkyl group which is optionally substitutedwith halo, phenyl or Si[Me]₃.

In a particular group of compounds of formula IV, Y is selected fromchloro or a (1-4C)alkyl group which is optionally substituted with halo,phenyl, or Si[Me]₃.

In a particular group of compounds of formula IV, Y is chloro, bromo ormethyl, especially chloro or methyl.

In an embodiment, the compound has the structural formula V shown below

wherein:

Y is as defined hereinbefore.

In an embodiment, the compound has the structural formula VI shown below

wherein:

X is as defined hereinbefore.

A particular compound of the invention is:

Particular examples of catalytic compounds of the invention include anyone of the following:

EBI*ZrCl₂;

EBI*HfCl₂;

EBI*TiCl₂;

EBI*ZrMe₂;

EBI*Zr(CH₂R)₂ (where R is phenyl, tertiary butyl or trimethylsilane);

EBI*HfMe₂; or

EBI*Hf(CH₂R)₂ (where R is phenyl, tertiary butyl or trimethylsilane).

and wherein EBI* is ethylene-bis-hexamethylindenyl.

The compounds of the present invention may be present in one or moreisomeric forms. In particular, the compounds of the present inventionmay be present as meso or rac isomers, and the present inventionincludes both such isomeric forms. A person skilled in the art willappreciate that a mixture of isomers of the compound of the presentinvention may be used for catalysis applications, or the isomers may beseparated and used individually (using techniques well known in the art,such as, for example, fractional crystallization).

Synthesis

The compounds of the present invention may be synthesised by anysuitable process known in the art. Particular examples of processes forthe preparing compounds of the present invention are set out in theaccompanying examples.

Suitably, a compound of the present invention is prepared by:

-   -   (i) reacting a compound of formula A:

-   -   (wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁, and R₁₂        are each as defined hereinbefore and M is Li, Na or K)    -   with a compound of the formula B:

X(Y′)₄  B

-   -   (wherein X is as defined hereinbefore and Y′ is halo        (particularly chloro or bromo)) in the presence of a suitable        solvent to form a compound of formula Ia:

-   -   and optionally thereafter:    -   (ii) reacting the compound of formula Ia above with MY″ (wherein        M is as defined above and Y″ is a group Y as defined herein        other than halo), in the presence of a suitable solvent to form        the compound of the formula Ib shown below

Suitably, M is Li in step (i) of the process defined above.

Suitably, the compound of formula B is provided as a solvate. Inparticular, the compound of formula B may be provided as X(Y)₄.THF_(p),where p is an integer (e.g. 2).

Any suitable solvent may be used for step (i) of the process definedabove. A particularly suitable solvent is toluene or THF.

If a compound of formula I in which Y is other than halo is required,then the compound of formula Ia above may be further reacted in themanner defined in step (ii) to provide a compound of formula Ib.

Any suitable solvent may be used for step (ii) of the process definedabove. A suitable solvent may be, for example, diethyl ether, toluene,THF, dicloromethane, chloroform, hexane DMF, benzene etc.

Processes by which compounds of the formula A above can be prepared arewell known art. For example, a process for the synthesis of a di-sodiumethylene-bis-hexamethylindenyl ligand of formula A is described in J.Organomet. Chem., 694, (2009), 1059-1068. A process for the synthesis ofa di-lithium ethylene-bis-hexamethylindenyl ligand of formula A isdescribed in the accompanying examples.

Compounds of formula A in which R₁ and R₇, R₂ and R₈, R₃ and R₉, R₄ andR₁₀, R₅ and R₁₁, R₆ and R₁₂ are the same, and Q is —CH₂—CH₂— maygenerally be prepared by:

-   -   (i) Reacting a compound of formula D

-   -   -   (wherein M is lithium, sodium, or potassium; and R₁, R₂, R₃,            R₄, R₅ and R₆ are as defined hereinbefore) with BrCN in the            presence of a suitable solvent to form a compound of formula            E shown below

-   -   -   and

    -   (ii) reacting a compound of formula E with C₁₀H₈.M in the        presence of a suitable solvent to form a compound of formula A.

Compounds of formula D can be readily synthesized by techniques wellknown in the art.

Any suitable solvent may be used for step (i) of the above process. Aparticularly suitable solvent is diethyl ether.

Similarly, any suitable solvent may be used for step (ii) of the aboveprocess. A suitable solvent may be, for example, toluene, THF, DMF etc.

For the avoidance of doubt, the C₁₀H₈.M reagent used in step (ii) of theabove process is lithium, sodium or potassium naphthalenide. In anembodiment, C₁₀H₈.M is sodium naphthalenide.

Applications

As previously indicated, the compounds of the present invention areextremely effective procatalysts for use in olefin polymerizationreactions.

Thus, the present invention also provides the use of a compound offormula I as defined herein as an olefin polymerization procatalyst, inparticular an ethylene polymerization catalyst.

The present invention also provides a process for forming a polyolefin(e.g. polyethylene) which comprises reacting the olefin monomers in thepresence of a compound of formula I as defined herein and a suitableactivator.

Suitable activators are well known in the art and include, but are notlimited to, aluminoxanes (e.g. methylaluminoxane) or triethylaluminium.

The catalyst compound of formula I may be applied to a suitable support.Examples of suitable supports include silica gels, aluminium oxides, orany other inorganic support materials.

It is possible to pre-activate the catalyst of formula I by mixing thecatalyst with the activator before use in the polymerisation reaction.Suitably, such pre-activation is carried out in solution, and typicallyin an inert hydrocarbon such as toluene.

Typically, the polymerisation reaction is carried out in a known mannerin solution, in suspension or in the gas phase, continuously, orbatchwise in one or more steps.

A person skilled in the art of olefin polymerization will be able toselect suitable reaction conditions (e.g. temperature, pressures,reaction times etc.) for such a polymerization reaction. A personskilled in the art will also be able to manipulate the processparameters in order to produce a polyolefin having particularproperties. For example, the temperature of such reactions could rangefrom −60 to 250° C. and the pressures may range from 0.5 to 100 bar, incertain circumstances.

In a particular embodiment, the polyolefin is polyethylene.

EXAMPLES

The invention will now be described in more detail in relation to thefollowing illustrative examples.

General Methodology

All organometallic manipulations were performed under an atmosphere ofN₂ using standard Schlenk line techniques or a MBraun UNIlab glovebox,unless stated otherwise. All organic reactions were carried out underair unless stated otherwise. Solvents used were dried by either refluxover sodium-benzophenone diketyl (THF), or passage through activatedalumina (hexane, Et₂O, toluene, CH₂Cl₂) using a MBraun SPS-800 solventsystem. Solvents were stored in dried glass ampoules, and thoroughlydegassed bypassage of a stream of N₂ gas through the liquid and testedwith a standard sodium-benzophenone-THF solution before use. Deuteratedsolvents for NMR spectroscopy of oxygen or moisture sensitive materialswere treated as follows: C₆D₆ was freeze-pump-thaw degassed and driedover a K mirror; d⁵-pyridine and CDCl₃ were dried by reflux over calciumhydride and purified by trap-to-trap distillation; and CD₂Cl₂ was driedover 3 Å molecular sieves.

¹H and ¹³C NMR spectroscopy were performed using a Varian 300 MHzspectrometer and recorded at 300 K unless stated otherwise. ¹H and ¹³CNMR spectra were referenced via the residual protio solvent peak. Oxygenor moisture sensitive samples were prepared using dried and degassedsolvents under an inert atmosphere in a glovebox, and were sealed inWilmad 5 mm 505-PS-7 tubes fitted with Young's type concentricstopcocks.

Mass spectra were using a Bruker FT-ICR-MS Apex III spectrometer.

For Single-crystal X-ray diffraction in each case, a typical crystal wasmounted on a glass fibre using the oil drop technique, withperfluoropolyether oil and cooled rapidly to 150 K in a stream of N₂using an Oxford Cryosystems Cryostream.²¹ Diffraction data were measuredusing an Enraf-Nonius KappaCCD diffractometer (graphite-monochromatedMoKa radiation, λ=0.71073 Å). Series of ω-scans were generally performedto provide sufficient data in each case to a maximum resolution of 0.77Å. Data collection and cell refinement were carried out usingDENZO-SMN.²² Intensity data were processed and corrected for absorptioneffects by the multi-scan method, based on multiple scans of identicaland Laue equivalent reflections using SCALEPACK (within DENZO-SMN).Structure solution was carried out with direct methods using the programSIR92²³ within the CRYSTALS software suite.²⁴ In general, coordinatesand anisotropic displacement parameters of all non-hydrogen atoms wererefined freely except where this was not possible due to the presence ofdisorder (i.e. toluene of crystallization in meso-2). Hydrogen atomswere generally visible in the difference map and were treated in theusual manner²⁵.

Polymerization trials and differential scanning calorimetry (DSC)experiments were run under industrial conditions. High temperature gelpermeation chromatography were performed using a Polymer LaboratoriesGPC220 instrument, with one PLgel Olexis guard plus two Olexis 30 cm×13μm columns. The solvent used was 1,2,4-trichlorobenzene withanti-oxidant, at a nominal flow rate of 1.0 mLmin⁻¹ and nominaltemperature of 160° C. Refractive index and Viscotek differentialpressure detectors were used. The data were collected and analysed usingPolymer Laboratories “Cirrus” software. A single solution of each samplewas prepared by adding 15 mL of solvent to 15 mg of sample and heatingat 190° C. for 20 minutes, with shaking to dissolve. The samplesolutions were filtered through a glass-fibre filter and part of thefiltered solutions were then transferred to glass sample vials. After aninitial delay of 30 minutes in a heated sample compartment to allow thesample to equilibrate thermally, injection of part of the contents ofeach vial was carried out automatically. The samples appeared to becompletely soluble and there were no problems with either the filtrationor the chromatography of the solutions. The GPC system was calibratedwith Polymer Laboratories polystyrene calibrants. The calibration wascarried out in such a manner that combined GPC-viscosity could be usedto give ‘true’ molecular weight data and conventional GPC could also beapplied. For the conventional GPC results, the system is calibrated withlinear polyethylene or linear polypropylene. This correction haspreviously been shown to give good estimates of the true molecularweights for the linear polymers.

For the GPC-viscosity approach, the system is still calibrated usingpolystyrene but the use of the refractive index (concentration) anddifferential pressure (viscosity) detector responses, together withaccurate knowledge of the polymer solution concentration, allowscomputation of ‘true’ molecular weight data without applying anycorrection. This approach also gives intrinsic viscosity data thatallows comparison of long chain branching. Although this approach doesgive ‘true’ molecular weight data, some parameters are adjusted toensure a good match for a known material and the approach used to obtainthe polymer sample concentration can be important. For this work, thedifferential refractive index (dn/dc) for the polyethylene/solventcombination was assumed and the concentration back calculated from therefractive index detector response. If samples were not simplypolyethylene, errors would be introduced due to a change in do/dc. Thedifferential pressure (viscosity) detector response is a function ofconcentration and intrinsic viscosity (effective molecular weight) andthe response to the propylene oligomer was too low for the applicationof the GPC-viscosity approach to be sensible.

Intermediate Preparation Preparation of ethylene-bis-hexamethylindenyl.EBI*Li₂.THF_(0.38); 1

Li (0.13 g, 1.86×10⁻² mol) and naphthalene (2.56 g, 2.00×10⁻² mol) werestirred in THF, forming a green solution after 3 hours which stillcontained Li and so was stirred for a further 15 hours. C₁₆H₂₀ (3.69 g,1.74×10⁻² mol) was dissolved in THF giving a bright yellow solution,which was added to the dark green C₁₀H₈Li mixture at −78° C. Thereaction mixture was stirred at −78° C. for 30 minutes then allowed towarm to room temperature with stirring. A precipitate formed after 2hours, and after a further 3 hours the solvent was removed under vacuumfrom the yellow-green mixture. The residue was washed with Et₂O anddried to yield an off white powder. Yield: 3.78 g, 93%. Analysis by NMRspectroscopy showed this solid to be of the formula EBI*Li₂.THF_(0.38),¹H NMR (d⁵-pyridine): δ 2.42, 2.45, 2.62, 2.89, 2.91 3.06 (all s, 6H,Me), 3.78 (s, 4H, C₂H₄). ¹³C NMR (d⁵-pyridine): δ 13.8, 16.3, 17.3,17.4, 18.7, 19.2 (Me), 36.4 (C₂H₄), 97.8, 105.6, 119.1, 119.4, 123.5,123.6, 124.8, 126.8, 128.8 (ring Cs).

Preparation of disodium ethylene-bis-hexamethlindenyl (EBI*Na₂)

(i) Synthesis of 2,3,4,5,6,7-hexamethyl-1-methylene-indene,C₁₆H₂₀

BrCN (2.89 g, 2.72×10⁻³ mol) was added under a N₂ flush to a −78° C.slurry in Et₂O of Ind*Li (6.00 g, 2.72×10⁻³ mol), prepared by aliterature procedure.¹ The reaction mixture was stirred at −78° C. for 2hours then allowed to warn to room temperature, upon which the off-whiteprecipitate dissolved to give a yellow solution. After stirring for 15hours under a dynamic pressure of N₂ to allow venting of HCN produced,volatiles were removed under vacuum. NMR analysis of the residuesoccasionally showed contamination of the desired product with anintermediate species, Ind*Br. Addition of Et₃N and further stirringconverted this into the fulvene compound C₁₆H₂₀. Extraction with 30° C.pentane, passing the resulting solution through silica and removal ofthe solvent under vacuum afforded2,3,4,5,6,7-hexamethyl-1-methylene-indene, C₁₆H₂₀ as a bright yellowsolid. Yield: 4.10 g, 71%.

Characterising Data:

¹H NMR (C₆D₆) δ (ppm): 1.91, 2.08 (both s, 3H, Me), 2.11 (s, 6H, Me),2.30, 2.36 (both s, 3H, Me), 5.56, 5.84 (both s, 1H, CH₂).

¹H NMR (CDCl₃) δ (ppm): 2.00, 2.23, 2.26, 2.28 (all s, 3H, Me), 2.45(bs, 6H, Me), 5.51, 5.88 (both s, 1H, CH₂).

¹³C NMR (C₆D₆) δ (ppm): 9.56, 15.53, 15.91, 16.03, 16.43, 16.64 (Me),28.84 (CH₂), 126.35, 129.45, 131.49, 131.61, 132.61, 132.22, 134.90,137.18, 140.37, 150.48 (ring Cs).

HRMS (EI): Calc: 212.1565. Found: 212.1567.

(ii) Synthesis of EBI*Na₂

Na (0.17 g, 7.56×10⁻³ mol) was stirred in THF with naphthalene (1.04 g,8.11×10⁻³ mol) for 15 hours, resulting in a deep green solution ofC₁₀H₈Na. After cooling to −78° C., a solution in THF of2,3,4,5,6,7-hexamethyl-1-methylene-indene (1.50 g, 7.06×10⁻³ mol) wasadded. The mixture was stirred for 2 hours at −78° C. and then allowedto warm to room temperature. Removal of the solvent under vacuumafforded a light brown solid, which was washed with Et₂O and filtered togive a light brown pyrophoric powder. Yield: 1.26 g, 76%.

Characterising Data:

¹H NMR (d₅-pyridine) δ (ppm): 2.49 (s, 12H, Me), 2.55, 2.71, 2.72, 3.13(all s, 6H, Me), 3.94 (s, 4H, C₂H₄).

¹³C NMR (d₅-pyridine) δ (ppm): 13.59, 16.41, 17.33, 17.46, 18.60, 19.05(Me), 35.06 (C₂H₄), 97.01, 104.27, 117.68, 118.07, 123.12, 123.17,123.77, 125.20, 125.79 (ring Cs).

The reaction mechanism for the above reaction is shown in Scheme 2below.

Example 1 Preparation of ethylene-bis-hexamethlindenyl zirconiumchloride (EBI*ZrCl₂)

EBI*Li₂.THF_(0.38) (0.350 g, 7.51×10⁻⁴ mol) was slurried in toluene andcooled to −78° C. To this orange-red slurry was added a white slurry ofZrCl₄.THF₂ (0.284 g, 7.51×10⁻⁴ mol) in toluene. No immediate change wasobserved and the reaction mixture was allowed to warm to roomtemperature with stirring. After stirring for a further 15 hours, thered-brown reaction mixture was filtered affording a red-orange solution.The residues were extracted with CH₂Cl₂ and the extracts combined.Removal of the solvent under vacuum gave a red-orange solid, which waswashed with −78° C. hexane. The resultant residue was extracted withroom temperature hexane to give a red-orange solid and yellow-orangesolution. NMR analysis of this solid showed it to be an approximately1:0.8 rac/meso mix. The solvent was removed under vacuum from theyellow-orange solution to give an orange solid; NMR analysis of thissolid indicated it to be mainly composed of meso-EBI*ZrCl₂ with a tinyproportion of impurities including the rac-isomer.

The rac/meso mix was extracted and filtered with CH₂Cl₂ to afford a redsolution which was layered with hexane. The yellow supernatant wasdecanted via cannula leaving an orange solid, shown by NMR analysis tobe pure rac-EBI*ZrCl₂. The supernatant was reduced under vacuum to anorange solid; a more meso enriched mixture of isomers; and washed with60° C. hexane, leaving pure rac isomer. The orange-yellow solution wasagain reduced to an isomeric solid mix, extracted with 60° C. hexane andcooled to −80° C., depositing a final crop of rac-EBI*ZrCl₂. Crystals ofrac-EBI*ZrCl₂ suitable for X-ray diffraction were grown as pale orangeplates by layering a CD₂Cl₂ solution of the sample with Et₂O.

The predominantly meso extracts were further extracted with 60° C.hexane and filtered, reduced to a minimum volume and cooled slowly to−35° C. Orange needles of pure meso-EBI*ZrCl₂ suitable for X-raydiffraction were collected and washed with −78° C. hexane.

Yield: 0.060 g, 0.028 g, total 20%.

Characterising Data:

HRMS (EI): Calc: 584.1554. Found: 584.1567.

rac-EBI*ZrCl₂:

¹H NMR (C₆D₆) δ (ppm): 1.78, 2.11, 2.22, 2.43, 2.46, 2.56 (all s, 6H,Me), 3.22-3.40, 3.70-3.88 (m, 4H, C₂H₄).

¹H NMR (CDCl₃) δ (ppm): 1.84, 2.23, 2.29, 2.33, 2.40, 2.79 (all s, 6H,Me), 3.65-3.81, 4.02-4.18 (m, 4H, C₂H₄).

¹H NMR (CD₂Cl₂) δ (ppm): 1.84, 2.24, 2.29, 2.31, 2.37, 2.80 (all s, 6H,Me), 4.03-4.22, 3.63-3.82 (m, 4H, C₂H₄).

¹³C NMR (CD₂Cl₂) δ (ppm): 11.96, 15.91, 16.58, 16.91, 17.71, 17.95 (Me),32.94 (C₂H₄), 115.97, 118.84, 123.56, 125.21, 126.40, 128.84, 129.46,130.65, 134.59 (ring Cs).

Anal. Calc for C₃₂H₄₀ZrCl₂: C, 65.50; H, 6.87. Found: C, 65.44; H, 6.79.

meso-EBI*ZrCl₂:

¹H NMR (C₆D₆) δ (ppm): 1.85, 1.99, 2.01, 2.39, 2.51, 2.52 (all s, 6H,Me), 3.20-3.34 3.74-3.88 (m, 4H, C₂H₄).

¹H NMR (CDCl₃) δ (ppm): 2.12, 2.13, 2.16, 2.32, 2.45, 2.60 (all s, 6H,Me), 3.63-3.80, 4.07-4.24 (m, 4H, C₂H₄).

¹H NMR (CD₂Cl₂) δ (ppm): 2.13 (s, 12H, Me), 2.17, 2.29, 2.43, 2.61 (alls, 6H, Me), 3.64-3.82, 4.08-4.26 (m, 4H, C₂H₄).

¹³C NMR (C₆D₆) δ (ppm): 13.27, 15.71, 16.51, 16.87, 17.59, 17.71 (Me),31.39 (C₂H₄), 106.72, 113.97, 121.50, 126.97, 127.29, 129.03, 130.68,132.98, 134.05 (ring Cs).

¹³C NMR (CDCl₃) δ (ppm): 13.45, 15.41, 16.45, 16.82, 17.40, 17.43 (Me),31.34 (C₂H₄), 104.09, 114.17, 121.62, 126.25, 126.75, 129.52, 130.21,133.03, 134.29 (ring Cs).

Structural Analysis of Rac-EBI*ZrCl₂

As stated above, single crystals of rac-EBI*ZrCl₂ suitable for X-raydiffraction were grown as pale orange plates by the layering of a samplein CD₂Cl₂ with Et₂O. The compound crystallises in the monoclinic spacegroup C2/c, and four alternate views are shown in FIG. 1. The compoundis located on a crystallographic twofold axis of rotation, hence bothindenyl rings are equivalent and relevant bond lengths and angles aregiven in Table 1 below.

TABLE 1 Selected bond lengths and angles for rac-EBI*ZrCl₂. Estimatedstandard deviations (ESDs) are given in parentheses. Lengths (Å)Zr(1)—C(3) 2.479(3) C(4)—C(14) 1.439(4) Zr(1)—C(4) 2.558(3) C(5)—C(10)1.430(4) Zr(1)—C(5) 2.612(3) C(10)—C(12) 1.385(4) Zr(1)—C(6) 2.582(3)C(12)—C(13) 1.432(4) Zr(1)—C(7) 2.520(3) C(13)—C(14) 1.382(4) C(3)—C(4)1.448(4) C(3)—C(18) 1.504(4) C(4)—C(5) 1.443(4) C(18)—C(18)* 1.546(6)C(5)—C(6) 1.437(4) Avg. C₅—Me 1.505 C(6)—C(7) 1.414(4) Avg. C₆—Me 1.514C(7)—C(3) 1.430(4) Zr(1)—Cp_(cent) 2.240 Zr(1)—Cl(2) 2.4358(7) Δ_(M-C)0.054 Angles (°) C₆—C₅ planes 2.6 δ 129.4 Cl(2)—Zr—Cl(2)* 96.24(4) HingeAngle 2.7 α α′ 57.2 55.6 Rotation Angle 124.4 β β′ −1.1 0.3

Structural Analysis of Meso-EBI*ZrCl₂

As stated above, X-ray quality crystals of meso-EBI*ZrCl₂ were obtainedas orange needles by the slow cooling of a concentrated hexane solutionto −35° C. The compound crystallises in the triclinic space group P 1,with one EBI* moiety and one toluene molecule per asymmetric unit.Alternate views are shown in FIG. 2, and relevant bond distances andangles are given in Table 2.

TABLE 2 Selected bond lengths and angles for meso-EBI*ZrCl₂. Estimatedstandard deviations (ESDs) are given in parentheses. Lengths (Å)Zr(1)—C(13) 2.470(5) Zr(1)—C(4) 2.627(5) Zr(1)—C(14) 2.557(5) Zr(1)—C(5)2.596(5) Zr(1)—C(15) 2.574(5) Zr(1)—C(6) 2.487(5) Zr(1)—C(16) 2.597(5)Zr(1)—C(7) 2.504(5) Zr(1)—C(17) 2.556(5) Zr(1)—C(8) 2.570(5) C(13)—C(14)1.442(8) C(4)—C(5) 1.441(7) C(14)—C(15) 1.438(8) C(5)—C(6) 1.448(8)C(15)—C(16) 1.436(8) C(6)—C(7) 1.422(8) C(16)—C(17) 1.402(8) C(7)—C(8)1.412(8) C(17)—C(13) 1.417(8) C(8)—C(4) 1.441(7) C(15)—C(20) 1.435(8)C(5)—C(28) 1.429(8) C(20)—C(22) 1.384(9) C(28)—C(29) 1.373(9)C(22)—C(23) 1.422(10) C(29)—C(31) 1.422(9) C(23)—C(24) 1.369(9)C(31)—C(32) 1.379(8) C(24)—C(14) 1.424(8) C(32)—C(4) 1.434(8)C(13)—C(12) 1.521(8) C(6)—C(11) 1.501(8) C(12)—C(11) 1.539(9) — Avg.C₅—Me 1.512 Avg. C₅—Me 1.508 Avg. C₆—Me 1.513 Avg. C₆—Me 1.513Zr(1)—Cp_(cent) 2.244 Hf(1)—Cp_(cent) 2.248 Zr(1)—Cl(2) 2.4276(13)Zr(1)—Cl(3) 2.4571(14) Δ_(M-C) 0.033 Δ_(M-C) 0.082 Angles (°) C₆—C₅planes 6.4 C₆—C₅ planes 3.9 Cl(2)—Zr—Cl(3) 97.41(5) — α α′ 56.9 54.4 — ββ′ 1.3 2.9 β β′ 1.0 1.9 δ 128.73 — Hinge Angle 6.0 Hinge Angle 3.3Rotation Angle 46.8 —

Example 2 Preparation of ethylene-bis-hexamethlindenyl hafnium chloride(EBI*HfCl₂)

To an orange-red slurry of EBI*Li₂.THF_(0.38) (0.350 g, 7.51×10⁻⁴ mol)in toluene at −78° C. was added a white slurry of HfCl₁.THF₂ (0.349 g,7.51×10⁻⁴ mol) in toluene. The reaction mixture was allowed to warm toroom temperature with stirring, with no observed change. After stirringfor 15 hours, an aliquot was taken and NMR analysis showed a 1.7:1 mixof meso/rac isomers. The yellow-brown reaction mixture was filtered, andthe remaining solid extracted with toluene and combined to give anorange-brown solution. Removal of the solvent under vacuum afforded ayellow-orange solid which was extracted with 60° C. hexane, giving abright yellow solution and buff powder, shown by NMR analysis to be a1:1 mix of rac/meso isomers. Removal of the solvent under vacuum fromthe bright yellow solution left a bright yellow solid, consisting by NMRanalysis of predominantly meso-EBI*HfCl₂ with a small amount of therac-isomer, and was purified to the pure meso form by extraction withroom temperature hexane and filtration.

The buff rac/meso mix was extracted with 60° C. hexane and filteredgiving a yellow solution, removal of the solvent under vacuum from whichgave a solid consisting of mainly the meso-isomer with a small impurityincluding the rac form. Another extraction of this solid with 60° C.hexane afforded a yellow solution plus yellow solid. This yellow solidwas dissolved in CH₂Cl₂, reduced to a minimum volume and layered withhexane. A light yellow solid precipitated and removal of the supernatantvia cannula left pure rac-EBI*HfCl₂. The second yellow hexane extractionwas reduced to a minimum volume and cooled to −35° C., whereupon abright yellow solid crop of meso-EBI*HfCl₂ was collected and washed with−78° C. hexane.

Single crystals of the meso form suitable for analysis by X-raydiffraction were grown as pale yellow plates by the cooling of asaturated isomerically pure hexane solution of meso-EBI*HfCl₂ to −35° C.X-ray diffraction quality crystals of the rac-isomer were obtained aspale yellow needles by the slow evaporation of an NMR pure C₆D₆ solutionof rac-EBI*HfCl₂.

Yield: 0.095 g, 0.057 g, total 30%.

Characterising Data:

MS (EI): Calc: 674.1957. Found: 674.1969.

rac-EBI*HfCl₂:

¹H NMR (C₆D₆) δ (ppm): 1.82, 2.12, 2.25, 2.46, 2.48, 2.55 (all s, 6H,Me), 3.43-3.52, 3.66-3.75 (m, 4H, C₂H₄).

¹H NMR (CDCl₃) δ (ppm): 1.88, 2.24, 2.31 (all s, 6H, Me), 2.38 (s, 12H,Me), 2.77 (s, 6H, Me), 3.83-3.94, 3.95-4.06 (m, 4H, C₂H₄).

¹H NMR (CD₂Cl₂) δ (ppm): 1.89, 2.26, 2.32, 2.34, 2.36, 2.79 (all s, 6H,Me), 3.85-3.94, 3.98-4.07 (m, 4H, C₂H₄).

¹³C NMR (CD₂Cl₂) δ (ppm): 11.49, 15.72, 16.17, 16.49, 16.82, 17.68 (Me),32.18 (C₂H₄), ring Cs not visible.

Anal. Calc for C₃₂H₄₀HfCl₂: C, 57.02; H, 5.98. Found: C, 57.08; H, 6.06.

meso-EBI*HfCl₂:

¹H NMR (C₆D₆) δ (ppm): 1.90, 2.01, 2.03, 2.39, 2.49, 2.57 (all s, 6H,Me), 3.23-3.40, 3.78-3.95 (m, 4H, C₂H₄).

¹H NMR (CDCl₃) δ (ppm): 2.13, 2.15, 2.22, 2.32, 2.51, 2.57 (all s, 6H,Me), 3.68-3.84, 4.11-4.27 (m, 4H, C₂H₄).

¹³C NMR (C₆D₆) δ (ppm): 13.19, 15.47, 16.43, 16.79, 17.57, 17.69 (Me),30.70 (C₂H₄), 110.79, 119.11, 125.30, 126.17, 126.33, 127.41, 130.46,132.74, 133.76 (ring Cs).

¹³C NMR (CDCl₃) δ (ppm): 13.72, 15.17, 16.36, 16.71, 17.38, 17.41 (Me),30.61 (C₂H₄), 110.91, 119.17, 124.88, 125.39, 126.47, 127.88, 129.97,132.77, 133.96 (ring Cs).

Characterisation of EBI*HfCl₂

Both isomers of EBI*HfCl₂ were characterised by ¹H and ¹³C NMRspectroscopy, MS, EA, single-crystal X-ray diffraction andelectrochemical studies. The ¹H NMR spectral data of rac andmeso-EBI*HfCl₂ were similar to those observed with rac andmeso-EBI*ZrCl₂, in a number of different solvents. This implies the Zrand Hf species also have similar structures in solution.

Structural Analysis of Rac-EBI*HfCl₂

As stated above, single crystals of rac-EBI*HfCl₂ suitable for X-raydiffraction were grown as pale yellow needles by the slow evaporation ofa C₆D₆ solution. The molecule crystallises in the monoclinic space groupC2/c, with 0.5 EBI* moieties per asymmetric unit. Four alternate viewsare shown in FIG. 3 and relevant bond distances and angles are given inTable 3.

As shown in Table 3 below, many structural parameters of rac-EBI*HfCl₂are very similar to those of the Zr analogue given in Table 1. The EBI*moiety bonds to the metal centre in a similar bis-η⁵ manner, thereplacement of the second row transition metal element with its smallerthird row equivalent resulting in an decrease in the M-Cp_(cent)distance of 0.018 Å. FIG. 3 clearly shows the large tilt angle α, andthe unusual negative value of β, as in rac-EBI*ZrCl₂

TABLE 3 Selected bond lengths and angles for rac-EBI*HfCl₂. Estimatedstandard deviations (ESDs) are given in parentheses. Lengths (Å)Hf(1)—C(3) 2.498(3) C(5)—C(12) 1.440(4) Hf(1)—C(4) 2.462(3) C(6)—C(9)1.433(4) Hf(1)—C(5) 2.541(3) C(9)—C(10) 1.379(4) Hf(1)—C(6) 2.598(3)C(10)—C(11) 1.441(4) Hf(1)—C(7) 2.571(3) C(11)—C(12) 1.378(4) C(3)—C(4)1.426(4) C(4)—C(41) 1.507(4) C(4)—C(5) 1.446(4) C(41)—C(41)* 1.554(6)C(5)—C(6) 1.448(4) Avg. C₅—Me 1.508 C(6)—C(7) 1.433(4) Avg. C₆—Me 1.511C(7)—C(3) 1.417(4) Hf(1)—Cp_(cent) 2.222 Hf(1)—Cl(2) 2.4118(7) Δ_(M-C)0.053 Angles (°) C₆—C₅ planes 2.5 δ 129.9 Cl(2)—Hf—Cl(2)* 95.43(4) HingeAngle 2.0 α α′ 57.0 55.9 Rotation Angle 125.2 β β′ −1.5 0.9

Structural Analysis of Meso-EBI*HfCl₂

As stated above, the slow cooling to −35° C. of a concentrated toluenesolution of meso-EBI*HfCl₂ afforded pale yellow plates suitable forstudy by X-ray diffraction. The compound crystallises in the monoclinicspace group P2₁/n, with one EBI* moiety in the asymmetric unit. Foralternate views are shown in FIG. 4, and selected bond distances andangles are given in Table 4.

TABLE 4 Selected bond lengths and angles for meso-EBI*HfCl₂. Estimatedstandard deviations (ESDs) are given in parentheses. Lengths (Å)Hf(1)—C(7) 2.562(6) Hf(1)—C(22) 2.453(5) Hf(1)—C(8) 2.459(5) Hf(1)—C(24)2.534(5) Hf(1)—C(9) 2.478(6) Hf(1)—C(30) 2.577(5) Hf(1)—C(11) 2.553(5)Hf(1)—C(31) 2.593(6) Hf(1)—C(12) 2.622(5) Hf(1)—C(32) 2.527(5) C(7)—C(8)1.436(8) C(22)—C(24) 1.438(8) C(8)—C(9) 1.402(8) C(24)—C(30) 1.446(7)C(9)—C(11) 1.428(8) C(30)—C(31) 1.437(8) C(11)—C(12) 1.432(8)C(31)—C(32) 1.415(8) C(12)—C(7) 1.445(8) C(32)—C(22) 1.428(8)C(12)—C(13) 1.421(8) C(24)—C(25) 1.429(8) C(13)—C(15) 1.371(9)C(25)—C(27) 1.378(8) C(15)—C(16) 1.439(10) C(27)—C(28) 1.423(9)C(16)—C(17) 1.374(9) C(28)—C(29) 1.389(9) C(17)—C(7) 1.450(8)C(29)—C(30) 1.418(8) C(8)—C(20) 1.511(8) C(22)—C(21) 1.519(7)C(20)—C(21) 1.551(9) — Avg. C₅—Me 1.511 Avg. C₅—Me 1.513 Avg. C₆—Me1.516 Avg. C₆—Me 1.515 Hf(1)—Cp_(cent) 2.225 Hf(1)—Cp_(cent) 2.226Hf(1)—Cl(2) 2.4215(13) Hf(1)—Cl(6) 2.3953(13) Δ_(M-C) 0.086 Δ_(M-C)0.030 Angles (°) C₆—C₅ planes 1.5 C₆—C₅ planes 2.3 Cl(2)—Hf—Cl(6)96.02(5) — α α′ 56.9 55.1 — β β′ 0.2 0.5 β β′ 0.9 2.1 δ 129.9 — HingeAngle 2.6 Hinge Angle 4.2 Rotation Angle 45.0 —

Example 3 Preparation of ethylene-bis-hexamethlindenyl titanium chlorideEBI*TiCl₂

EBI*Li₂.THF_(0.38) (0.075 g, 1.61×10⁻⁴ mol) was slurried in toluene andcooled to −78° C. To this buff slurry was added a bright blue solutionof TiCl₃.THF₃ (0.060 g, 1.61×10⁻⁴ mol) in THF. The reaction mixture wasobserved to darken, and on warming to room temperature a red-brownsolution was obtained. The reaction mixture was stirred for a further 15hours at room temperature, then transferred via cannula onto a slurry ofPbCl₂ (0.030 g, 1.05×10⁻⁴ mol) in THF. The reaction mixture changed to ayellow-green colour, and a dark grey solid was seen on the bottom of theSchlenk, presumed to be Pb. The reaction mixture was stirred for another15 hours and left to settle, affording a green-yellow solution with darkgrey solid and a dark grey metallic rim at the solvent edge. Filtrationand removal of the solvent under vacuum left a dark green solid, shownby NMR analysis to contain peaks consistent with EBI*TiCl₂ together withEBI*H₂ and fulvene peaks. The residue was washed with hexane, dissolvedin a minimum volume of toluene and the green solution cooled to −78° C.A solid precipitated and was collected by filtration, washed with −78°C. toluene, NMR analysis showing it to be consistent with the formula ofthe desired product EBI*TiCl₂. Yield: 0.009 g, 10%.

Characterising Data:

rac-EBI*TiCl₂

MS (EI): Calc: 542.1987. Found: 542.1994.

¹H NMR (C₆D₆) δ (ppm): 1.70, 2.11, 2.23, 2.46, 2.47, 2.59 (all s, 6H,Me), 3.25-3.42, 3.86-4.03 (m, 4H, C₂H₄).

¹H NMR (CDCl₃) δ (ppm): 1.74, 2.25, 2.32, 2.35, 2.40, 2.84 (all s, 6H,Me), 3.74-3.90, 4.26-4.42 (m, 4H, C₂H₄).

¹H NMR (d₈-toluene) δ (ppm): 1.68, 2.11, 2.21, 2.40, 2.42, 2.60 (all s,6H, Me), sample too weak to assign C₂H₄ multiplet accurately.

Example 4 Preparation of EBI*ZrMe₂

rac-EBI*ZrCl₂ was suspended in Et₂O and cooled to −78° C. To this orangesuspension was added an excess of 1.56M MeLi.LiBr in Et₂O, and thereaction mixture allowed to warm to room temperature. The initial orangesuspension became a yellow solution and was stirred for a further 2hours. Removal of the solvent under vacuum, extraction with hexane andremoval of the volatiles afforded a light orange-yellow solid, shown byNMR analysis to be meso-EBI*ZrMe₂. The use of low halide MeLi in Et₂Owith rac-EBI*ZrCl₂ was found to yield rac-EBI*ZrMe₂. A similar procedurewas followed with meso-EBI*ZrCl₂ and 1.56M MeLi.LiBr in Et₂O, affordingmeso-EBI*ZrMe₂.

Characterising Data:

rac-EBI*ZrMe₂:

¹H NMR (C₆D₆) δ (ppm): −0.99 (s, 6H, Zr-Me), 1.69, 2.12, 2.22, 2.41,2.49, 2.51 (all s, 6H, Me), 3.12-3.29, 3.41-3.58 (m, 4H, C₂H₄).

meso-EBI*ZrMe₂:

¹H NMR (C₆D₆) δ (ppm): −2.33, −0.20 (both s, 3H, Zr-Me), 1.77, 2.04,2.07, 2.41, 2.42, 2.48 (all s, 6H, Me), 2.95-3.12, 3.53-3.70 (m, 4H,C₂H₄).

¹H NMR (CDCl₃) δ (ppm): −2.88, −0.62 (both s, 3H, Zr-Me), 2.03, 2.11,2.14, 2.38, 2.39, 2.48 (all s, 6H, Me), 3.23-3.38, 3.68-3.83 (m, 4H,C₂H₄).

Example 5 Preparation of EBI*Zr(CH₂R)₂ (where R is phenyl, tertiarybutyl or trimethylsilane)

To an NMR tube containing a suspension of rac-EBI*ZrCl₂ in C₆D₆ wasadded an excess of either KCH₂Ph, LiCH₂SiMe₃ or LiCH₂ ¹Bu. The tube wassonicated for 10 minutes and the NMR spectrum acquired. In the caseswith KCH₂Ph and LiCH₂SiMe₃, initial NMR analysis indicated the reactionwas instantaneous, forming meso-EBI*(CH₂Ph)₂ and rac-EBI*Zr(CH₂SiMe₃)₂respectively. The reaction of rac-EBI*ZrCl₂ with LiCH₂ ¹Bu initiallyshowed some starting materials to remain, however after being left for15 hours NMR analysis indicated complete conversion to rac-EBI*Zr(CH₂^(t)Bu)₂.

Characterising Data:

meso-EBI*Zr(CH₂ ^(t)Bu)₂:

¹H NMR (C₆D₆) δ (ppm): −2.19, 0.43 (both s, 2H, Zr—CH₂ ^(t)Bu), 0.59,1.40 (both s, 9H, CH₂CMe₃), 1.96, 2.13, 2.15, 2.47, 2.52, 2.60 (all s,6H, Me), 3.00-3.11, 3.60-3.71 (m, 4H, C₂H₄).

rac-EBI*Zr(CH₂SiMe₃)₂:

¹H NMR (C₆D₆) δ (ppm): −1.73, −0.21 (both d, 2H, J=10.50 Hz, Zr—CH₂TMS),0.09 (s, 18H, CH₂SiMe₃), 1.80, 2.12, 2.24, 2.46, 2.53, 2.57 (all s, 6H,Me), 3.12-3.31, 3.39-3.58 (m, 4H, C₂H₄).

meso-EBI*Zr(CH₂Ph)₂:

¹H NMR (C₆D₆) δ (ppm): −0.72, 1.82 (both s, 2H, Zr—CH₂Ph), 1.84, 2.00(both s, 6H, Me), 2.03 (s, 12H, Me), 2.40, 2.49 (both s, 6H, Me),2.98-3.16, 3.58-3.76 (m, 4H, C₂H₄), 6.39, 6.57 (both d, 2H, J=6.6 Hz,CH₂C₆H₂ ^(othro)H₂ ^(meta)H^(para)), 6.80, 6.94 (both t, 1H, CH₂C₆H₂^(ortho)H₂ ^(meta)H^(para)), 7.05, 7.13, (both t, 2H, CH₂C₆H₂ ^(ortho)H₂^(meta)H^(para)).

Example 6 Preparation of EBI*HfMe₂

rac-EBI*HfCl₂ was dissolved in Et₂O, cooled to −78° C. and an excess of1.56M MeLi.LiBr in Et₂O added, the mixture becoming lighter in colour.After stirring for 2 hours, the solvent was removed under vacuum.Extraction with hexane afforded a light yellow solution, and removal ofthe solvent under vacuum a light yellow solid shown by NMR analysis tobe rac-EBI*HfMe₂.

meso-EBI*HfCl₂ was treated in the same way, the hexane extracts beingalmost colourless and removal of the solvent under vacuum affording anoff-white solid. This was shown by NMR analysis to be meso-EBI*HfMe₂.

Characterising Data:

rac-EBI*HfMe₂:

¹H NMR (C₆D₆) δ (ppm): −1.18 (s, 6H, Hf-Me), 1.70, 2.12, 2.23, 2.41,2.49, 2.53 (all s, 6H, Me), 3.28-3.36, 3.42-3.50 (m, 4H, C₂H₄).

meso-EBI*HfMe₂:

¹H NMR (C₆D₆) δ (ppm): −2.59, −0.39 (both s, 3H, Hf-Me), 1.83, 2.04,2.07, 2.41, 2.42, 2.46 (all s, 6H, Me), 3.03-3.20, 3.58-3.75 (m, 4H,C₂H₄).

¹³C NMR (C₆D₆) δ (ppm): 13.12, 14.44, 16.35, 16.68, 17.47, 17.55 (Me),29.88 (C₂H₄), 92.85, 106.04, 110.34, 123.92 (ring Cs), other ring Cs notvisible.

Example 7 Preparation of EBI*Hf(CH₂R)₂ (where R is Phenyl, TertiaryButyl or Trimethylsilane)

To an NMR tube containing an orange solution of rac-EBI*HfCl₂ in C₆D₆was added an excess of either KCH₂Ph, LiCH₂SiMe₃ or LiCH₂ ^(t)Bu. Thetube was sonicated for 10 minutes and the NMR spectrum obtained, showingcomplete conversion to rac-EBI*Hf(CH₂R)₂.

A bright yellow solution of meso-EBI*HfCl₂ in C₆D₆ was treated with anexcess of either KCH₂Ph, LiCH₂SiMe₃ or LiCH₂ ^(t)Bu. After sonicationfor 10 minutes the NMR spectrum was obtained. Reaction with KCH₂Ph wasinstantaneous; those with LiCH₂SiMe₃ and LiCH₂ ^(t)Bu showed a mixtureof meso-EBI*HfCl₂ and the desired product, and were left for a further15 hours. NMR analysis of these samples showed complete conversion tomeso-EBI*Hf(CH₂SiMe₃)₂ and meso-EBI*Hf(CH₂ ^(t)Bu)₂ respectively.

Characterising Data:

rac-EBI*Hf(CH₂ ^(t)Bu)₂:

¹H NMR (C₆D₆) δ (ppm): −1.36, −0.20 (both d, 2H, J=11.70 Hz, Hf—CH₂^(t)Bu), 1.00 (s, 18H, CH₂CMe₃), 1.93, 2.16, 2.25, 2.51, 2.55, 2.58 (alls, 6H, Me), sample too weak to assign C₂H₄ multiplet accurately.

meso-EBI*Hf(CH₂ ^(t)Bu)₂:

¹H NMR (C₆D₆) δ (ppm): −2.49, 0.08 (both s, 2H, Hf—CH₂ ^(t)Bu), 0.59,1.40 (both s, 9H, CH₂CMe₃), 2.01, 2.13, 2.15, 2.49, 2.50, 2.67 (all s,6H, Me), 3.06-3.22, 3.61-3.77 (m, 4H, C₂H₄).

rac-EBI*Hf(CH₂SiMe₃)₂:

¹H NMR (C₆D₆) δ (ppm): −1.95, −0.53 (both d, 2H, J=12.00 Hz,Hf—CH₂SiMe₃), 0.09 (s, 18H, CH₂SiMe₃), 1.81, 2.12, 2.25, 2.48, 2.53,2.57 (all s, 6H, Me), sample too weak to assign C₂H₄ multipletaccurately.

meso-EBI*Hf(CH₂SiMe₃)₂:

¹H NMR (C₆D₆) δ (ppm): −3.32, −0.64 (both s, 2H, CH₂SiMe₃), 2.00, 2.07,2.16, 2.44, 2.53, 2.59 (all s, 6H, Me), 3.00-3.27, 3.52-3.79 (m, 4H,C₂H₄), CH₂SiMe₃ peaks obscured by residual LiCH₂SiMe₃ resonances.

rac-EBI*Hf(CH₂Ph)₂:

¹H NMR (C₆D₆) δ (ppm): −0.36, 1.17 (both d, 2H, J=12.30 Hz, Hf—CH₂^(t)Bu), 1.67, 1.79, 2.15, 2.17, 2.31, 2.58 (all s, 6H, Me), 3.28-3.45,3.48-3.65 (m, 4H, C₂H₄), 6.80-7.20 (m, 10H, CH₂Ph).

meso-EBI*Hf(CH₂Ph)₂:

¹H NMR (C₆D₆) δ (ppm): −0.92, 1.61 (both s, 2H, Hf—CH₂Ph), 1.94, 1.99,2.01, 2.10, 2.39, 2.48 (all s, 6H, Me), 3.05-3.24, 3.62-3.81 (m, 4H,C₂H₄), 6.37, 6.72 (both d, 2H, J=7.2 Hz, CH₂C₆H₂ ^(ortho)H₂^(meta)H^(para)), 6.77, 6.96 (both t, 1H, CH₂C₆H₂ ^(ortho)H₂^(meta)H^(para)), 7.06, 7.17 (both t, 2H, CH₂C₆H₂ ^(ortho)H₂^(meta)H^(para)).

Example 8 Ethylene Polymerisations

The homogenous ethylene polymerisation activity of the catalystsprepared in examples 1 and 2 was evaluated. The catalysts were dissolvedin toluene with half the modified methylaluminoxane (MMAO) activatoradded in this solution (5000 equivalents vs metal), and the other halfadded in the 5 L steel autoclaves. The polymerisation conditions andresults are summarised in Table 5.

TABLE 5 Homogenous ethylene polymerisation conditions and resultsobtained with rac and meso-EBI*MCl₂ (M = Zr, Hf) Catalyst Run PolymerProductivity Catalyst amount MMAO time yield (g) (g_(PE)/mol met/h)rac-EBI*ZrCl₂ 1.17 mg 20 mmol 15 min 309 6.18 × 10⁸ meso-EBI*ZrCl₂ 2μmol Zr 10000 eq/Zr 30 min 382 3.83 × 10⁸ rac-EBI*HfCl₂ 1.35 mg 20 mmol60 min 25 1.25 × 10⁷ meso-EBI*HfCl₂ 2 μmol Hf 10000 eq/Hf 67 3.35 × 10⁷

-   -   Polymerisation conditions: 1.8 L isobutene, 70° C., P_(C2)=10        bar

As shown in Table 5, both rac and meso Zr compounds are very active inethylene polymerisation, with catalytic activities obtained between3×10⁸ and 6×10⁸ g_(PE)/mol Zr/h. The Hf analogues are less active, by afactor of approximately 49 for the rac compounds and approximately 11for the meso forms. In the case of EBI*ZrCl₂, the rac isomer wasapproximately 1.6 times more active than the meso; this trend isreversed in EBI*HfCl₂, with the meso form being 2.7 times more activethan the rac.

Comparative studies on the catalytic performance of other Group 4metallocene compounds generally agree with the activity of Zr complexesbeing substantially higher than that of the corresponding Hf compoundsunder similar conditions.²⁻⁴ Studies have been performed into theelectronic and steric effects of the ligands, together with thepolymerisation conditions, on the ethylene polymerisation activities ofzirconocene catalysts.⁵⁻⁸ The role of the aluminoxane co-catalyst hasbeen examined, and for most homogenous metallocene catalysts a largeexcess of aluminoxane is required for the polymerisation to achieve itsoptimum productivity. The literature commonly reports Al/Zr ratiosbetween 1000 to 50000, with activity generally increasing as the ratioincreases, up to an optimal value. It is therefore important whencomparing activity data to compare similar conditions and Al/Zr ratioswhere possible. MAO is the most commonly used aluminoxane, however ithas been shown that MMAO/metallocene and MAO/metallocene systems havecomparable polymerisation rates, hence values in this work can bereadily compared with the literature.⁹

The effect of ligand substitution on the polymerisation activity hasbeen rationalised on steric grounds, with unsubstituted zirconocenedichloride being more active than mixed sandwiches which are in turnmore active than symmetrically substituted compounds, as shown in Table6. The Me groups have a sterically hindering effect and decrease theflexibility towards the spatial requirements of the incoming monomer andthe growing polymer chain.

TABLE 6 Ethylene polymerisation data, showing negative steric effect oncatalytic activity of Cp based zirconocenes/MAO systems, together withactivities of EBI* species in the same units Activity Catalyst(kg_(PE)/g_(Zr)/h) Al/Zr ratio Ref. Cp₂ZrCl₂ 500 8000:1 18 ^(a)(CpMe₄H)CpZrCl₂ 255 8000:1 18 ^(a) Cp*CpZrCl₂ 170 8000:1 18 ^(a)(CpMe₄H)₂ZrCl₂ 135 8000:1 18 ^(a) Cp*₂ZrCl₂ 135 8000:1 18 ^(a)rac-EBI*ZrCl₂ 6775 10000:1  This invention ^(b) meso-EBI*ZrCl₂ 418710000:1  This invention ^(b) ^(a) 70° C., P_(C2) = 5 bar; ^(b) 70° C.,P_(C2) = 10 bar

It can also be seen from Table 6 that, although the Al/Zr ratio isslightly higher for the EBI*ZrCl₂ samples, the activity is significantlygreater than for all the Cp based Zr systems.

The data in Table 7 show that the unbridged Ind species Ind₂ZrCl₂ isapproximately 3.7 times more active than Cp₂ZrCl₂. Furthermore, theyindicate that the introduction of an ansa bridge in this Ind casereduces the activity of the resulting catalyst by almost 7 times to avalue similar to that of Cp*₂ZrCl₂. These trends of decreasing activitywith increasing steric substitution, and decreased activity of bridgedcompared with non-bridged species, has also been documented elsewhere inthe literature.¹⁰

TABLE 7 Ethylene polymerisation data for a series of Cp and Ind basedzirconocene catalysts Activity Catalyst (kg_(PE)/g_(Zr)/h) Al/Zr ratioRef. Cp₂ZrCl₂ 185 4000:1 18 ^(a) Cp*₂ZrCl₂ 95 4000:1 18 ^(a) Ind₂ZrCl₂686 5000:1 19 ^(b) rac-EBIZrCl₂ 102 5000:1 19 ^(b) ^(a) 70° C., P_(C2) =5 bar; ^(b) 50° C., P_(C2) = 2 bar

The data in Table 6 and Table 7 suggest that, even though information atequivalent Al/Zr ratios is not available, the EBI*ZrCl₂ catalysts aremuch more active than either the Cp based, unbridged Ind, or ansa Zrspecies given here. It appears that the EBI* ligand array counters theusual trends, being both ansa bridged and fully substituted yet alsohighly active.

As mentioned earlier, experimentally determined values of catalystactivity are highly dependent upon the precise reaction conditions, andoften the kinetic profile or lifetime of the catalyst is not mentioned.However, to enable comparison of values in the literature, Gibsonsuggests converting activity figures to a g_(polymer)/mmol metal/h/bar,and placing the catalyst on a scale of merit ranging from very low tovery high. This scale is shown in Table 8, together with the convertedvalues for the EBI*MCl₂ species tested.¹²

TABLE 8 Qualitative performance assignment for catalyst activities,together with converted values for EBI*MCl₂ species Activity(g_(polymer)/mmol met/h/bar) Performance Very low less than 1 Low  1-10Moderate 10-10² High 10²-10³  Very high greater than 10³ Catalystrac-EBI*ZrCl₂ 6.18 × 10⁴ meso-EBI*ZrCl₂ 3.82 × 10⁴ rac-EBI*HfCl₂ 1.25 ×10³ meso-EBI*HfCl₂ 3.35 × 10³

According to this scheme, each of the four EBI* catalysts tested have avery high activity rating in ethylene polymerisation. Under similarconditions (Al/Zr ratio 8300:1, 50° C., P_(C2)=2 bar) Ind₂ZrCl₂ andrac-EBIZrCl₂ have been reported to have activities of 1.40×10⁴ and1.30×10⁴ g_(PE)/mmol Zr/h/bar respectively.¹³ rac-EBI*ZrCl₂ surpassesthis maximum activity by a factor of approximately five.

Samples of each polymer produced by EBI*MCl₂ catalysts were analysed bydifferential scanning calorimetry (DSC) in order to determine theirmelting points, and values obtained are shown in Table 9.

TABLE 9 Melting points of polyethylene samples prodcuced, measured byDSC Melting point of Catalyst polyethylene produced (° C.) rac-EBI*ZrCl₂133.16 meso-EBI*ZrCl₂ 133.75 rac-EBI*HfCl₂ 134.59 meso-EBI*HfCl₂ 132.03

It can be seen that each of the four polyethylene samples analysed has asimilar melting point. There is slightly more variation between thesamples produced by the Hf catalysts than those produced by rac andmeso-EBI*ZrCl₂. For comparison, the literature reports that polyethylenesynthesised by meso-EBIZrCl₂ catalyst has a melting point determined byDSC of 123° C., compared with 135° C. for that of theracanalogue.^(13,14) This reduction in melting point has been attributed tothe introduction of short branches into the polyethylene chain and theformation of linear low-density polyethylene (LLDPE). However, a numberof other polyethylene samples produced via ansa bridged substituted mesozirconocene catalysis show a melting point of approximately 133° C.¹⁵ Ingeneral the melting points of EBI* catalysed polyethylene samples arecomparable with those in the literature for non-branched, linearhigh-density polyethylene (HDPE).¹⁶

For comparison of their molecular weight distributions and a comparisonof chain branching, each polyethylene sample has been further analysedby high temperature gel permeation chromatography (GPC); using bothcombined GPC-viscosity and conventional GPC approaches. The GPC systemwas calibrated in such a manner that combined GPC-viscosity could beused to give ‘true’ molecular weight data and conventional GPC couldalso be applied, results from the latter expressed as for linearpolyethylene. GPC-viscosity was not used for the polypropylene oligomersince the viscosity detector response is effectively a function ofmolecular weight, hence the response to the propylene oligomer sample istoo low for this technique to be sensible. These data are summarised inTable 10 as the calculated molecular weight averages (weight averagemolecular weight M_(w), number average molecular weight M_(n)) andpolydispersities (M_(w)/M_(n)).

TABLE 10 Molecular weight averages and polydispersities (M_(w)/M_(n))for the four polyethylene samples produced, data obtained by hightemperature GPC and combined GPC-viscosity, with duplicate runsperformed for each sample Catalyst Technique M_(w) M_(n) M_(w)/M_(n)rac-EBI*ZrCl₂ GPC 215000 88800 2.4 215000 91200 2.4 GPC-viscosity 21700083200 2.6 216000 85000 2.5 meso-EBI*ZrCl₂ GPC 203000 86100 2.4 20300086400 2.4 GPC-viscosity 202000 80000 2.5 202000 79900 2.5 rac-EBI*HfCl₂GPC 228000 85600 2.7 227000 85100 2.7 GPC-viscosity 228000 79800 2.9225000 77700 2.9 meso-EBI*HfCl₂ GPC 106000 33700 3.2 107000 34800 3.1GPC-viscosity 103000 34200 3.0 103000 35200 2.9

It can clearly be seen from Table 10 that three of the four polyethylenesamples have similar molecular weight distributions, however the sampleproduced by the meso-EBI*HfCl₂ catalyst is of considerable lowermolecular weight (approximately half) and has the broadest distribution.Within the other three samples, there are small but clear differences;the polymer produced with rac-EBI*HfCl₂ as catalyst has the highestweight average molecular weight (M_(w)) and broadest distribution, whilethat from meso-EBI*ZrCl₂ has the lowest M. Although the M_(w) and M_(n)of the Zr catalysed samples are different, their polydispersities areidentical. Within Hf catalysed samples, a similar effect is observed inpolydispersities in the combined GPC-viscosity data. It appears that forboth Zr and Hf catalysed polyethylene samples, the polymers with thehighest M_(w) are those of the rac rather than the meso catalysts. Byreference to Table 9 it can be seen that there exists a correlationbetween the highest values of M_(w), M_(n) and melting point for therac-EBI*HfCl₂ catalysed polymer, and the lowest values of M_(w), M_(n)and melting point for the resultant meso-EBI*HfCl₂ polyethylene.

It has been noted in the literature that molecular weight distributionsof polymers obtained in ethylene polymerisation studies vary with thereaction conditions, making direct quantitative comparisons betweenpreviously published results difficult.^(17,16) However, values of M_(w)and polydispersity of EBI*MCl₂ catalysed polymers are similar to thosefound in the literature.^(7,8,17) Some reported values of activity,M_(w) and polydispersity for a number of metallocene catalysedpolyethylene samples are given in Table 11.

TABLE 11 Comparison of activity, M_(w) and polydispersity (M_(w)/M_(n))for select Zr and Hf Ind catalysts in ethylene polymerisation Activity(kg_(PE)/mol Al/Zr M_(w) M_(w)/ Catalyst met/h) ratio (×10³) M_(n) Ref.Ind₂ZrCl₂ 62500  5000:1 490 2.3 19 ^(a) Ind₂HfCl₂ 7812  5000:1 959 2.619 ^(a) rac-EBIZrCl₂ 9377  5000:1 240 3.2 19 ^(a) rac-EBIHfCl₂ 2101 5000:1 387 4.4 19 ^(a) rac- 2100 10000:1 200 3.2 20 ^(b) EBIOSiZrCl₂rac- 200 10000:1 280 3.3 20 ^(b) EBIOSiHfCl₂ rac- 2500 10000:1 >1000 2-420 ^(b) EBTHIOSiZrCl₂ rac-EBI*ZrCl₂ 618000 10000:1 217 2.6 Thisinvention ^(c) meso-EBI*ZrCl₂ 382000 10000:1 202 2.5 This invention ^(c)rac-EBI*HfCl₂ 12500 10000:1 227 2.9 This invention ^(c) meso-EBI*HfCl₂33500 10000:1 103 3.0 This invention ^(c) ^(a) 50° C., P_(C2) = 2 bar;^(b) 40° C., P_(C2) = 2.5 bar, IOSi = 2-OSiMe₂ ^(t)Bu-indenyl; ^(c) 70°C., P_(C2) = 10 bar

In general, Hf catalysts are less active than their Zr analogues, andpolymers obtained with Hf catalysts show a higher molecular weight thanthe corresponding Zr species under similar conditions.²⁻⁴ However, inthe case of EBI*MCl₂, the meso Hf species seems unusual in this regardin that it has a dramatically lower M. The data in Table 11 show thatthe ansa bridged Ind species produce polymers with much lower M_(w) thanthe unbridged analogues. The values of M_(w) for the polymers producedby rac-EBIZrCl₂ and rac-EBI*ZrCl₂ are similar, however the M_(w) of therac-EBI*HfCl₂ catalysed sample is also lower than anticipated, despitebeing greater than its Zr catalysed analogue. It has been found thatchanging the catalyst type dramatically affects the M_(w), with M_(w)values increasing in the orderEBIZrCl₂<Cp₂ZrCl₂<Cp₂HfCl₂<Cp₂TiCl₂<EBTHIZrCl₂.¹⁷ Furthermore, the samestudy found increases in MAO concentrations to decrease averagemolecular weight. It is not unexpected therefore that the M_(w) valuesfor the EBI* species studied are the lowest in Table 11.

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What is claimed is:
 1. A compound of the formula I shown below

wherein: R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂ are eachindependently hydrocarbyl, carbocyclyl or heterocyclyl, each of which isoptionally substituted by halo, amino, nitro, cyano, (1-6C)alkyl,(1-6C)alkoxy, (1-6C)alkylamino, [(1-6C)alkyl]₂amino, or—S(O)_(r)(1-6C)alkyl wherein r is 0, 1 or 2; Q is a bridging groupcomprising 1, 2 or 3 bridging atoms; X is zirconium, titanium orhafnium; and each Y group is halo, hydride, a phosphonated orsulphonated anion, or a (1-6C)alkyl, (1-6C)alkoxy, aryl or aryloxy groupwhich is optionally substituted with halo, nitro, amino, phenyl,(1-6C)alkoxy, or Si[(1-4C)alkyl]₃.
 2. The compound according to claim 1,wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂ are eachindependently (1-6C)alkyl or phenyl, each of which is optionallysubstituted by halo, amino, nitro, cyano, (1-6C)alkyl, (1-6C)alkoxy,(1-6C)alkylamino, [(1-6C)alkyl]₂amino, or —S(O)_(r)(1-6C)alkyl, whereinr is 0, 1 or
 2. 3. The compound according to claim 2, wherein R₁, R₂,R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂ are all methyl.
 4. Thecompound according to claim 3, wherein Q is a group of the formula—[C(R^(a)R^(b))]_(n)— wherein n is 2 or 3 and R^(a) and R^(b) are eachindependently hydrogen, (1-6C)alkyl or (1-6C)alkoxy.
 5. The compoundaccording to claim 4, wherein Q is —CH₂—CH₂— or —CH₂—CH₂—CH₂—.
 6. Thecompound according to claim 5, wherein Q is —CH₂—CH₂—.
 7. The compoundaccording to claim 1, wherein X is zirconium or hafnium.
 8. The compoundaccording to claim 1, wherein Y is halo, (1-6C)alkyl or phenyl, whereinthe alkyl or phenyl group is optionally substituted with halo, nitro,amino, phenyl, (1-6C)alkoxy, or Si[(1-4C)alkyl]₃.
 9. The compoundaccording to claim 8, wherein Y is halo or a (1-2C)alkyl group which isoptionally substituted with halo, phenyl, or Si[(1-4C)alkyl]₃.
 10. Thecompound according to claim 1, wherein each Y group is the same.
 11. Thecompound according to claim 1, wherein the compound has the structuralformula II shown below

and R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁, R₁₂, X and Y are asdefined in claim
 1. 12. The compound according to claim 1, wherein thecompound has the structural formula IV shown below

and X and Y are as defined in claim
 1. 13. The compound according toclaim 1, wherein the compound has the structural formula:


14. A process of preparing a compound according to claim 1, comprising:reacting a compound of formula A:

wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁, and R₁₂ are eachas defined in claim 1 and M is Li, Na or K; with a compound of formulaB:X(Y′)₄  B wherein X is as defined in claim 1 and Y′ is halo; in thepresence of a suitable solvent to form a compound of formula Ia:

and optionally thereafter: reacting the compound of formula Ia with MY″,wherein M is Li, Na or K and Y″ is a group Y as defined in claim 1 otherthan halo, in the presence of a suitable solvent to form a compound offormula Ib shown below


15. A pro-catalyst for the polymerisation of olefins comprising acompound of formula I prepared according to the process of claim
 14. 16.A process for forming a polyolefin which comprises reacting olefinmonomers in the presence of a compound of formula I according to claim 1and a suitable activator.
 17. The process according to claim 16, whereinthe activator is an aluminoxane or triethylaluminium.
 18. The processaccording to claim 17, wherein the polyolefin is polyethylene.
 19. Theprocess of claim 14, wherein Y′ is chloro or bromo.
 20. The process ofclaim 17, wherein the aluminoxane is methylaluminoxane.